The present disclosure is related to equipment used during subterranean formation operations and, more particularly, to composite slickline cables including optical fibers that enable functionality diagnostics for reliable subterranean operations and services.
Hydrocarbons are typically produced from wellbores drilled from the Earth's surface through a variety of producing and non-producing subterranean zones. The wellbore may be drilled substantially vertically or may be drilled as a lateral well that has some amount of horizontal displacement from the surface entry point. A variety of servicing operations may be performed in the wellbore, such as mechanical intervention services and formation property evaluations, after it has been drilled by lowering different kinds of downhole tools into the wellbore. For example, measuring instruments are commonly lowered into the wellbore to obtain various downhole conditions, such as depth-dependent formation pressure and temperature, formation porosity, fluid viscosity, and density. Various sampling and/or logging devices are also commonly lowered into the wellbore to either analyze fluid samples in-situ at various target zones of the subterranean formation or extract formation fluids for surface laboratory analysis.
Such servicing operations are typically undertaken by lowering the downhole tool into the wellbore on a wireline cable or a slickline cable. Specifically, slickline cables are either single-strand or multi-strand wires or cable that often contain energy transmission conductors (e.g., optical fibers, electrical wires, acoustic transceivers, etc.) or other electrical components commonly used in oil or gas operations. Slickline cables can be made of stainless steel, or other metal and alloy materials, but have more recently been made of fiber-reinforced polymer composite based materials, which may improve toughness and exhibit increased resistance to fatigue and corrosion over metal slickline cables. Another advantage of a polymer composite material based slickline cable is its lighter weight could enable services in deeper onshore and offshore wells.
A polymer composite material based slickline cable is required to have sufficient tensile strain capability or mechanical strength to support both the weight of the downhole tool and the slickline cable, and also have sufficient strength to perform mechanical services. The characteristics of traditional slickline cables, in combination with the extreme conditions of subterranean environments, may increase the likelihood that such cables fail due to mechanical fatigue, wearing, and transient overloading stress. For example, wellbores experience temperatures varying from ambient at surface to in excess of 150° C. (302° F.), and hydraulic pressures up to 137.9 MPa (20,000 psi). These conditions may increase both thermal and mechanical strains on the polymer composite slickline cable, which make it possible for wellbore fluids (e.g., hydrocarbon fluids or gases, water, etc.) to penetrate fiber-reinforced composite based slickline cables, and the like, causing delamination or crack-based structural defects in the cable. Catastrophic failure of the slickline cable will occur when its effective loading capability is lower than the applied loading tensile strain.
Since a slickline cable is reused multiple times throughout its lifetime, it is common to monitor the structural integrity of the slickline cable, which may be particularly difficult to do since slickline cables often extend up to and surpass 30,000 feet in length. Traditional non-destructive techniques to inspect and determine slickline cable integrity include laser ultrasonic, thermography, microwave, terahertz, radio frequency (RF), eddy current, and x-ray radiography techniques. Such non-destructive inspections, however, only analyze surface defects, or result in only a representative portion of the slickline cable being evaluated, and not the entire length of the cable. Moreover, traditional non-destructive inspections are more adequate in laboratory settings, rather than in field use.